Method and apparatus for twisting wires

ABSTRACT

An apparatus and method is disclosed for producing a set of wires in which each wire defines a helical path about the longitudinal axis of the set, the apparatus comprises flexible elongated guide means, for example, nylon tubes; the apparatus enables a set to be produced in which the number of reversals in the path of a wire in a set is reduced; there is also disclosed a cable and an apparatus and method of making it comprising a bundle of sets as defined above.

United States Patent Forester Nov. 12, 1974 [54] METHOD AND APPARATUS FOR 3.448569 6/1969 Brown cl a] 57/15 TWISTING WIRES FOREIGN PATENTS OR APPLICATIONS [75] lnvemorl Glen Robe" Forester, Burnaby, 726,565 12/1966 ltaly 140/149 British Columbia, Canada [73} Assignee: Phillips Cable Limited, West Primary Examiner-Lowell A. Larson Brockville, Ontario, Canada Attorney. Agent, or Firm-Di|ler, Brown, Ramik & 1221 Filed: Dec. 19, 1972 wght 1211 Appl. N6: 316,542 [57] ABSTRACT I 1 An apparatus and method is disclosed for producing a [2% ps. Cll. 140/l49,257/77.3 Set of wires in which each wire defines a helical path l C 1f about the longitudinal axis of h Set the apparatus [58] Fled of Search 140/115, 149, 57/77.3, comprises flexible elongated guide means, for exam,

174/32 34 ple, nylon tubes; the apparatus enables a set to be produced in which the number of reversals in the path of [56] References C'ted a wire in a set is reduced; there is also disclosed a U IT STATES PATENTS cable and an apparatus and method of making it com- 2,546,977 4/1951 Clary, Jr. et al. 57/58.55 prising a bundle of sets as defined above. 3,053,039 9/1962 Demmel 57/35 3,l69,360 2/1965 Corrall 6t 21] 57 77.3 17 Clams 9-Drawmg Flgures I inllllil:

PATENTEDNuv 12 I974 sum 5 or 5 BACKGROUND OF THE INVENTION a. Field of the Invention This invention relates to a method and apparatus for twisting wires and to a method and apparatus for forming a bundle of wires comprising a plurality of sets of v twisted wires and to such a bundle of wires.

More especially it is concerned with a method and apparatus for making electric cables which consist of or comprise a layer of wires which extend about a central axis, which may comprise a core, in a helical path which periodically reverses in direction. Thus the cable may comprise or consist of a plurality of wires twisted together to form a set such that each wire describes a helical path about the longitudinal axis of the set and in which the helical path periodically reverses in direction; the invention relates further to a method and apparatus for making an electric cable comprising a bundle of such sets of twisted conductors.

In this specification a wire includes a single electric conductor whether bare or insulated, and a group of two or more electric conductors whether bare or separately orcollectively insulated, for example, a twisted telephone pair or a quad.

The term core when used in this specification means a single wire either bare or insulated, or a group of wires associated in any manner, which may or may not be enclosed within a common envelope.

b. Description of Prior Art Manufacture of a cable comprising or consisting of a plurality of electric conductors twisted together to form sets such that each conductor describes a helical path about the longitudinal axis of the set which reverses in direction periodically, can be effected by passing the conductors from their supply bobbins through a fixed lay plate and to and through an oscillating lay plate spaced apart from the fixed lay plate. In this case the oscillating lay plate oscillates angularly up to 360 about the longitudinal axis of the set. The twisted conductors leaving the oscillating lay plate pass to a closing die where the twist is held.

If the oscillating lay plate is rotated more than 360 in either direction then the section of the wires passing SUMMARY OF THE INVENTION The present invention has an object to provide a method and apparatus for manufacture of cables of the kind described, in which an angle of oscillation greater than 360 may be used without damage to the electric conductors due to their rubbing against each other during the travel of the electric conductors from a fixed plate to the point at which the twisted cable is formed.

The invention further provides an apparatus and method for producing a set of twisted together wires in which the direction of twist reverses periodically in direction, and in which a relatively large number of twists can be produced in one direction without a change in direction. This means that for a given length of a set of twisted together wires, there can be fewer reversal points.

According to the invention apparatus for twisting a plurality of wires to form a set in which each wiredefines a helical path about the longitudinal axis of the set comprises flexible elongated guide means for the wires, said guide means being twistingly rotatable about said longitudinal axis through an angle greater than 360 relative to the untwisted wires.

According to another feature of the invention the apparatus further includes first and second spaced apart housing means for the guide means, said first housing means being adapted to support one end of the guide means and said second housing means being adapted to twistingly rotate the guide means through an angle greater than 360 relative to the first housing.

According to another aspect of the invention a method of twisting wires comprises passing a plurality of wires from a fixed pathway to and through flexible elongated guide means, rotating said guide means through an angle greater than 360 relative to the untwisted wires about the longitudinal axis of the set of twisted wires to be formed, thereby forming a set of twisted wires in which each wire defines a helical path about the longitudinal axis of the set.

By means of the'apparatus and method according to the invention, a cable of the type which consists of or comprises a layer of wires, which extend about a central axis in a helical path, which periodically reverses in direction can be produced having a greater number of twists following each other in the same direction for a given speed of the wire through the apparatus and for a given speed of rotation of the twisting apparatus.

According to another aspect of the invention a method of forming a bundle of wires comprising a plurality of sets of twisted together wires, comprises: twisting wires together to form a plurality of sets in such a way that each wire in a set defines a helical path about the longitudinal axis of theset, said helical path reversing periodically in direction, and feeding said plurality of sets together to produce the bundle.

According to another feature of this aspect of the invention the wires of at least some sets are given a different twist from the wires of other sets so that the wires of at least some sets of wires in the bundle have a nonparallel relationship with the wires of other sets of wires in the bundle.

According to another feature of this aspect of the invention twist holding means is applied to each set substantially at the point where the direction of the helical path of each wire in a set is reversed in direction.

According to another feature of this aspect of the invention the twist holding means comprises an adhesive means for example, glue, adhesive tape or polybutene.

According to another feature of this aspect of the invention the plurality of sets of wires is twisted together to form a twisted bundle.

According to another feature the method of forming a bundle comprises passing a plurality of groups of wires from fixed pathways to and through a plurality of flexible elongated guide means, rotating said guide means through an angle greater than 360 relative to the untwisted wires about the respective longitudinal axis of the corresponding set of twisted wires to be formed, to form said plurality of sets.

According to another aspect of the invention apparatus for forming a bundle of wires comprising a plurality of sets of twisted together wires comprises: means for twisting wires together to form a plurality of sets in such a way that each wire in a set defines a helical path about the longitudinal axis of the set, said helical path periodically reversing in direction, and means for feeding said plurality of sets together to produce the bundle.

According to another feature of this aspect of the invention the means for twisting comprises flexible elons gated guide means for the wires for each set to be formed, said guide means being twistingly rotatable about the respective longitudinal axis of the corresponding set to be formed through an angle greater than 360 relative to the untwisted wires.

According to another feature of this aspect of the invention the means for twisting the wires of at least one set further includes first and second spaced apart housing means for the guide means, said first housing means being adapted to support one end of the guide means and said second housing means being adapted to twistingly rotate the guide means through an angle of greater than 360 relative to the first housing.

According to another feature of this aspect of the invention the apparatus further includes means for applying twist holding means to each set substantially at the points where the direction of the helical path of each wire in'a set is reversed in direction.

BRIEF DESCRIPTION OF DRAWINGS A preferred embodiment of the invention is illustrated with reference to the accompanying drawings in which:

FIG. 1 illustrates a pairof wires or twin having a reverse twist,

FIG. 2 illustrates a pair of wires or twin having a different reverse twist,

FIG. 3 illustrates apparatus for twisting a pair of wires together to produce a twin,

FIG. 4 illustrates schematically apparatus .for producing a bundle of three sets of twins,

FIG. 5 illustrates schematically apparatus for producing a cable,

FIG. 6 illustrates schematically another apparatus for producing a cable,

FIG. 7 illustrates schematically another apparatus for producing a cable,

FIG. 8 is a cross-section of a cable produced using the apparatus of FIG. 7,

FIG. 9 illustrates schematically an apparatus for producing a cable comprising sets of twisted together wires in which some sets have a non-parallel relationship with other sets.

DESCRIPTION OF PREFERRED EMBODIMENTS With reference to FIG. 1 a wire pair having a reverse twist comprises wires 21 and 22, the point 23 being the point of reversal of twist; the portion 24a is provided with a right-hand twist and the portion 24b is provided with a left-hand twist.

With reference to FIG. 2 a wire pair 20a having a reverse twist comprises wires 21a, 22a, the points 23a and 23b being points of reversal of twist, the portions 240 and 24d being provided with a right-hand twist and the portion 24e being provided with a left-hand twist.

In this wire pair 20a, there are thus two points of reversal 23a and 23b; the amount of twist or the pitch of the portions 24c and 24d being substantially identical and different from the amount of twist or pitch in portion 24e.

With reference to FIG. 3 apparatus 1 for producing cables comprises tubular guides 2 of a low friction material, for example, nylon, housed at one end in a housing 3 mounted for oscillatory movement in a bearing 4 and at the other end in a housing 5.

The housing 3 comprises a cylindrical wall 6 and a side wall 8, one end of the housing 3 being open.

The side wall 8 has holes or bores 10 therein, one for each of the tubular guides 2 which pass therethrough.

The housing 5 comprises a block 11 having bores 12 passing between end walls 13 and 14 respectively to accommodate each of the tubular guides 2.

The tubular guides 2 are arranged to pass through the bores 12 in the housing 5 and the holes or bores 10 in the housing 3. Each of the tubular guides 2 has lips 15 and 16 at its extreme ends. The lips 15 and 16 abut against the end wall 13 of the housing 5 and the side wall 8 of the housing 3 respectively and retain the ends of the tubular guides 2 outside of the housings 3 and 5.

In operation electric conductors 17 pass through the tubular guides 2. On emerging from the housing 3 the conductors 17 may pass to a holding means, where necessary having regard to the nature of the wires, which may be, for example, a closing die (not shown) which .holds the conductors 17 in the configuration in which they emerge from the housing 3, alternatively if the cable is to be sheathed the conductors may pass to a sheathing station, and in this case the sheathing 0f the conductors serves to hold them in the configuration in which they emerge from the housing 3.

During the passage of the electric conductors 17 through the tubular guides 2 the housing 3 is rotated in its bearing 4 about the axis 18 through an angle greater than 360. This rotation of the housing 3 results in the tubular guides 2 being twisted together within the housing 3 and the electric conductors l7 being twisted on their emergence from the housing 3.

When the housing 3 has been rotated several times in one direction thereby resulting in a twist in the tubular guides 2 and in the electric conductors 17 emerging from the housing 3, in a first direction the rotation is reversed; this has the effect of untwisting the tubular guides 2 and then twisting them in a second direction opposite to the first twisting direction.

The degree of twist in the tubular guides 2'will depend upon the angle through which the housing 3 is rotated, and it has been found thatthe housing 3 can be rotated several times in one direction without difficulty. Clearly the length of the housing 3 is of significance. If the distance between housing 5 and the side wall 8 is comparatively short in length, then the length of the tubular guides 2 which can be twisted will be correspondingly less and so a fewer number of successive rotations of the housing 3 in one direction can be made.

The degree of twist in the electric conductors 17 will depend on both the speed of travel of the conductors through the tubular guides 2 and the speed of rotation of the housing 3.

The lips and 16 at the ends of the tubular guides 2 may be fixed to the end wall 13 and the side wall 8 respectively, and in this case, there should be sufficient slack in the tubular guides 2 to allow them to be twisted a number of times, or the tubular guides 2 should be of an elastic material, which will stretch and thereby facilitate the twisting. Alternatively the lips 15 and 16 may simply abut against the end wall 13 and the side wall 8 and be free to move away therefrom.

The apparatus 1 has been illustrated with two tubular guides 2, however the invention is not limited to two and there may suitably be a greater number as desired, a useful number of tubular guides 2 is from two to twenty-five.

The tubular guides 2 are preferably of a material having a low coefficient of friction, to allow the guides 2 to slide easily against one another.

It is also within the scope of the invention to twist the electric conductors 17 about a wire core 19. In this case the wire core 19 would suitably be fed along the axis 18 through passages 26 and 27 in housings 5 and 3 respectively.

With reference to FIG. 4 a plurality of wires 30 may be continuously withdrawn from supply reels 31 by suitable means for example, a capstan (not shown) and is advanced to apparatus 1, which may be of the kind illustrated with reference to FIG. 3 where the wires 30 are twisted into pairs 32 with a reverse twist. The twisted pairs 32 advance through a die former 33, which brings the pairs 32 together to form a unit 34, which passes to a rotating take-up reel 35. The take-up reel 35 may optionally oscillate 0r rotate unidirectionally about a radial axis of the reel to twist the unit 34 to produce a stranded unit 36 in which the pairs 32 are twisted together with a reversing twist or a twist in one direction respectively.

The pairs 32 may be given different amounts of twist per unit length by suitably adjusting the rate of oscillation of apparatus 1, so that the wires of different pairs 32 will have a non-parallel relationship. Also the twist in a pair 32 may be varied as illustrated in FIG. 2 by varying the rate of oscillation of the apparatus 1 through which the wires 30 of a pair pass.

In addition the two described effects can be combined so that the amount of twist varies within a pair 32 and also between different pairs 32.

With reference to FIG. 5, the apparatus is essentially similar to that described with reference to FIG. 4, except that the take-up reel 35 is replaced by an oscillating capstan 37, which oscillates to produce a twist in the stranded unit 34, and a binding head 38, taping head 39 and extruder 40 are included.

In the binding head 38 the stranded unit 34 is bound with a binder 41, for example, string to hold the stranded unit compactly.

The taping head 39 winds a tape 42 around the stranded unit 34; the tape 42 may be of a material, which will act as an electrical shield, for example, aluminium tape, or it may be any other conventional tape for cables, for example, paper tape or polyethylene tape.

The extruder 40 extrudes a jacket of insulating material, for example, polyethylene, around the taped unit to produce a cable 43.

It will be apparent that the amount of twist per unit length in the pairs 32 can be varied, and that the amount of twist may be different in different pairs 32 as described with reference to FIG. 4.

With reference to FIG. 6, wires 60 may be continuously withdrawn from supply reels 61 by suitable means, for example, a capstan (not shown), and are advanced to apparatus 62 similar to apparatus 1 illustrated in FIG. 3, but having three tubular guides 2. The wires 60 are twisted together with a reverse twist in the manner described with referenceto FIG. 3 to form a set 63, which is advanced to. an extruder 64 in which a jacket of insulating material is extruded around it to produce a cable 65.

With reference to FIG. 7, there is illustrated an apparatus for making a power cord of the kind shown as Type S, which is used, for example, in electrically operated tools. A plurality of wires a, 70b and 70c may be withdrawn continuously from supply reels 71a, 71b and 710 by suitable means, for example, capstans (not shown) and are advanced to apparatus 72a, 72b and 72c, where they are twisted to form sets 73a, 73b and 73c having a reverse twist.

The sets 73a, 73b and 73c are passed through extruders 74a, 74b and 74c respectively, where they are each provided with a cover of an insulating material, for example, polyethylene. The insulated sets 75a, 75b and 75c are then advanced together to an extruder 76, where they are jacketed with an insulating material, for example, polyethylene, to produce a cable 78.

In the embodiment illustrated in FIG. 7 various modifications are possible. The apparatus 72a, 72b and 720 may be of the type illustrated in FIG. 3, but having a greater number of guide tubes 2. This apparatus is much preferred, since it allows for a greater number of twists in one direction before reversal is necessary, and it is relatively simple. However, more conventional apparatus may be used particularly if the number of reversals per unit length is not too important.

Also, in the apparatus illustrated in FIG. 7, it is possible to produce a'cable 78 in which one or all of the sets 73a, 73b and 73c has a different amount of twist or pitch from the others. To achieve this, the wires 70a, 70b and 70c would be advanced at the same rate, but the rate of oscillation of, for example, 7 2b would be different from the rate of oscillation of 72a and 72c.

With reference to FIG. 8, a cable 78 produced using the apparatus illustrated in FIG. 7 comprises jacketed sets 75a, 75b and 75c surrounded by a jacket 79. As set 75b is conventionally a ground wire, it may in some cases be permissible to omit the insulation and the associated extruder 74b.

With reference to FIG. 9 apparatus for producing a cable core 100 comprises twisting units a, 90b and 90c, which may be of the kind illustrated with reference to FIG. 3 for the embodiment illustrated in FIG. 9, there would be 4 tubular guides 2 in each unit 90a, 90b and 900; however, the number of tubular guides 2 in each twisting unit will be dependent on the number of wires 91a, 91b, 910. Also, there might be a greater number than four of wires 91a, 91b and 910 respectively and generally the number of wires 91b would be greater than the number of wires 91a and the number i of wires 91c would be greater than the number of wires from that of 90a so that the lay is'different in each layer. Set 93a retains its identity passing centrally through the twisting unit 90b while wires 91b pass through tubular guides similar to tubular guides 2 in FlG. 3. On emerging from twisting unit 90b, wires 91b are twisted around set 93a with a reversing twist to produce a set 93b in which the set 93a is a core.

A third plurality of wires 91c is withdrawn continuously from supply reels 920 by suitable means, and is advanced to twisting unit 900. Set 93b is advanced to twisting unit 900 at the same rate as wires 91c, but the rate of oscillation of twisting unit 900 may be different from that of 90b so that the lay is different in each layer.

Set 931) retains its identity passing centrally through the twisting unit 90c while wires 91c pass through tubular guides similar to tubular guides 2 in FIG. 3. On emerging from twisting unit 900, wires 910 are twisted around set 93b with a reversing twist to produce a cable core 100 in which the set 931) is a core.

The cable core may pass through further operations, for example, the operations described with reference to FIG. 5.

Further, the amount of twist per unit length produced by each of twisting units 90a, 90b and 90c may be the same or different, and the amount of twist produced by each of twisting units 90a, 90b and 900 may vary as described with reference to FIGS. 2 and 4.

In an example, with reference to FIG. 3, four tubular guides 2 made of nylon were used, these being 4.5 feet in length and 0.25 inches in diameter. The tubular guides 2 were threaded through a tubular steel housing 3, the housing 3 being 4 feet long and 1 inch in diameter. lnsulated electric conductors 17 having a diameter of 0.060 inches were fed through the tubular guides 2 at a speed of 300 ft./min. and the housing 3 was rotated for l0 revolutions in a first direction at a speed of 360 revs/min. after which it was stopped and rotated at a speed of 360 revs/min. in the reverse direction for 20 revolutions and so on for 20 revolutions.

A cable was thus produced having 360/300 twists per foot, i.e. a 10 inch lay. The first part of the cable, i.e. the part comprising the conductors 17, which first emerged from the housing 3, will have half the number of twists in one direction as the following cable, i.e. if the first part of the cable has n twists in one direction, the second part of the cable will have 2n twists in the reverse direction, and there will then be successively 2n twists in each direction.

As described above, it is also within the scope of the invention to have two or more apparatus 1 each having two or more wires passing therethrough to form several twisted pairs or sets, the twisted pairs or sets then being brought together and optionally twisted to form a unit, and a number of units being optionally twisted together and sheathed to form a large cable. in this case the pairs or sets might each be given a different amount of twist in the two or more apparatus 1, so that the wires of different pairs or sets in a unit would not be parallel. This is advantageous in telephone cables, since if the pairs or sets of wires are parallel, there will be induction between the pairs or sets which results in crossover during a telephone conversation. If the pairs or sets are brought together and optionally twisted together in a non-parallel fashion then'inductance between pairs and hence cross-over is diminished.

In this embodiment the twist produced in eachpair of wires as it emerges from its housing 3 in the apparatus 1 of FIG. 3 may be held by the application of a small amount of glue to the twisted together wires immediately before the direction of rotation of housing 3 and hence direction of twist is changed. Polybutene has been found to be particularly useful for holding the end twist in a twisted pair prior to the formation of twist in the reverse direction.

It will be apparent that if the twist is not held, as by gluing, that when the direction of rotation of housing 3 is changed, the twisted wires may be untwisted. Generally some form of twist holding means is desirable unless the twisted wires are passed immediately to a further operation, for example, a sheathing operation, which would additionally serve as twist holding means. However, the necessity for twist holding means will also depend on the nature of the wires. For example, for polyethylene insulated copper wires normally encountered in the telephone industry, there is substantially no tendency for the opposing twists to cancel each other, and therefore, the wires do not revert to an untwisted state. However, where a reversing twist is to be applied to relatively resilient wires, the twisted wires may be taped, wrapped, or otherwise held as indicated above to prevent cancellation of the opposing twists.

It is further within the scope of the invention for a case in which several tubular guides 2 are housed in a housing 3 to forin the holes or bores 10 into groups of two or more concentric circles; in this case, a first group of conductors 17, which pass through the'inner concentric circle of holes or bores 10 are twisted together with a reverse twist. A second group of conductors 17 passes through the circle of holes or bores 10 adjacent the inner circle, and are twisted together with a reverse twist about the first group of twisted together conductors, which form a core for the second group.

Thus, a cable can be produced from a single apparatus 1 comprising a plurality of layers of conductors 17 twisted together with a reverse twist; the number of layers being limited only by the number of concentric circles of holes or bores 10 in the housing 3.

I claim:

1. An apparatus for the continuous production of an electric cable comprising a set of twisted together electric conductor wires in which each wire defines a helical path about the longitudinal axis of the set which reverses periodically in direction in a predetermined manner, which comprises an entrance housing and spaced apart therefrom an exit housing; a plurality of flexible elongated tubular sleeves continuous from end to end of a low friction material; said apparatus having a longitudinal axis about which said wires are twisted through an angle greater than 360; said sleeves being entrained from end to end between and supported at their ends by said housings; said entrance housing being rigidly mounted and said exit housing being mounted for oscillatory movement about said longitudinal axis of said apparatus to twistingly rotate the sleeves through an angle greater than 360; and means for continuously feeding electric conductor wires to and through said tubular sleeves as the sleeves are twistably rotated.

2. A method of continuously producing an electric cable comprising a set of electric conductor wires twisted together in which each wire defines a helical path about the longitudinal axis of the set which reverses periodically in direction in a predetermined manner which comprises:

a. continuously feeding a plurality of wires from a fixed pathway to and through a plurality of flexible elongated sleeves continuous from end to end of a low friction material such as nylon, said sleeves being entrained from end to end between and supported at their ends in a stationary housing and an oscillatable housing, said wires entering said sleeves adjacent said stationary housing and emerging from said sleeves adjacent said oscillatable housing,

b. rotating said oscillatable housing about said longitudinal axis of the set to be formed through an angle greater than 360 relative to the untwisted wires in a first direction to produce a first portion of said set having a twist in one direction, in said wires emerging from said sleeves,

c. applying a twist holding means to said first portion and d. reversing the direction of rotation of said oscillatable housing and rotating the oscillatable housing in such reverse direction through an angle greater than 360 to produce a second portion of said set adjacent the first portion, having a twist in a second direction counter to the said first direction.

3. A method according to claim 2 wherein a core wire is fed between said sleeves along the longitudinal axis of the set to be formed, said set being formed around said core.

4. Apparatus according to claim 1 and further including holding means adapted to hold the set in its twisted configuration.

5. Apparatus according to claim 1 wherein said exit housing has a plurality of bores defined therein in two or more concentric circles, said sleeves being retained in said bores.

6. A method according to claim 2 in which the oscillatable housing is oscillated a plurality of times through an angle greater than 360, thereby producing a set in which the helical path of each wire in the set reverses periodically in direction in a predetermined manner.

7. A method according to claim 6 in which the speed of rotation of the oscillatable housing is changed when the direction of rotation is reversed whereby the helical path of the wires in one direction is different from the helical path of the wires in the other direction.

8. A method according to claim 2 in which the ends of the sleeves are supported on the circumferences of a plurality of imaginary concentric circles having their centres on the longitudinal axis of the set of wires to be formed, whereby a set is formed comprising a core of wires twisted together in which each wire defines a helical path about the longitudinal axis of the core which reverses periodically in direction, and a plurality of layers of wires twisted together in which each wire defines a helical path about the core which reverses periodically in direction, the number of said layers being one less than the number of concentric circles.

9. A method according to claim 2 in which twist holding means is applied to the set to retain the twist in the set as the oscillatable housing is rotated in said second direction.

10. A method according to claim 2 including the further step of feeding a plurality of such sets together to form a bundle.

11. A method according to claim 10 wherein the wires of at least some sets are given a different twist from the wires of other sets, so that the wires of at least some sets of wires in the bundle have a non-parallel relationship with the wires of other sets of wires in the bundle.

12. A method according to claim 11 wherein the pinrality of sets is twisted together to form a twisted buntile.

13. A method according to claim 10 wherein a sheath of insulating material is extruded around each set to form a plurality of sheathed sets,

the sheathed sets are fed together into an extrusion apparatus and a jacket of insulating material is extruded around the sheathed sets.

14. A method according to claim 10 wherein one of said plurality of sets provides a core and the other of said plurality of sets form layers around said core.

15. A unit for the continuous production of an electric cable comprising a bundle of sets of twisted together electric conductor wires inwhich each wire in a set defines a helical path about the longitudinal axis of the set which reverses periodically in direction in a predetermined manner, which comprises a plurality of devices each having an entrance housing and spaced apart therefrom an exit housing; a plurality of flexible elongated tubular sleeves continuous from end to end of a low friction material; each device having a longitudinal axis about which said wires are twisted through an angle greater than 360; said sleeves being entrained from end to end between and supported at their ends by said housings; said entrance housing being rigidly mounted and said exit housing being mounted for oscillatory movement about said longitudinal axis of each said device to twistingly rotate the sleeves through an angle greater than 360; means for continuously feeding electric conductor wires to and through said tubular sleeves as the sleeves are twistably rotated said devices being aligned so that the sets emerging from said devices can be fed together, and means for feeding said sets together to form a bundle.

16. Unit according to claim 15 including means for applying twist holding means to each set substantially at the points where the direction of the helical path of each wire in a set is reversed in direction.

17. Unit according to claim 15 including means for twisting the plurality of sets together to form a twisted bundle. 

1. An apparatus for the continuous production of an electric cable comprisinG a set of twisted together electric conductor wires in which each wire defines a helical path about the longitudinal axis of the set which reverses periodically in direction in a predetermined manner, which comprises an entrance housing and spaced apart therefrom an exit housing; a plurality of flexible elongated tubular sleeves continuous from end to end of a low friction material; said apparatus having a longitudinal axis about which said wires are twisted through an angle greater than 360*; said sleeves being entrained from end to end between and supported at their ends by said housings; said entrance housing being rigidly mounted and said exit housing being mounted for oscillatory movement about said longitudinal axis of said apparatus to twistingly rotate the sleeves through an angle greater than 360*; and means for continuously feeding electric conductor wires to and through said tubular sleeves as the sleeves are twistably rotated.
 2. A method of continuously producing an electric cable comprising a set of electric conductor wires twisted together in which each wire defines a helical path about the longitudinal axis of the set which reverses periodically in direction in a predetermined manner which comprises: a. continuously feeding a plurality of wires from a fixed pathway to and through a plurality of flexible elongated sleeves continuous from end to end of a low friction material such as nylon, said sleeves being entrained from end to end between and supported at their ends in a stationary housing and an oscillatable housing, said wires entering said sleeves adjacent said stationary housing and emerging from said sleeves adjacent said oscillatable housing, b. rotating said oscillatable housing about said longitudinal axis of the set to be formed through an angle greater than 360* relative to the untwisted wires in a first direction to produce a first portion of said set having a twist in one direction, in said wires emerging from said sleeves, c. applying a twist holding means to said first portion and d. reversing the direction of rotation of said oscillatable housing and rotating the oscillatable housing in such reverse direction through an angle greater than 360* to produce a second portion of said set adjacent the first portion, having a twist in a second direction counter to the said first direction.
 3. A method according to claim 2 wherein a core wire is fed between said sleeves along the longitudinal axis of the set to be formed, said set being formed around said core.
 4. Apparatus according to claim 1 and further including holding means adapted to hold the set in its twisted configuration.
 5. Apparatus according to claim 1 wherein said exit housing has a plurality of bores defined therein in two or more concentric circles, said sleeves being retained in said bores.
 6. A method according to claim 2 in which the oscillatable housing is oscillated a plurality of times through an angle greater than 360*, thereby producing a set in which the helical path of each wire in the set reverses periodically in direction in a predetermined manner.
 7. A method according to claim 6 in which the speed of rotation of the oscillatable housing is changed when the direction of rotation is reversed whereby the helical path of the wires in one direction is different from the helical path of the wires in the other direction.
 8. A method according to claim 2 in which the ends of the sleeves are supported on the circumferences of a plurality of imaginary concentric circles having their centres on the longitudinal axis of the set of wires to be formed, whereby a set is formed comprising a core of wires twisted together in which each wire defines a helical path about the longitudinal axis of the core which reverses periodically in direction, and a plurality of layers of wires twisted together in which each wire defines a helical path about the core which reverses periodically in direction, the number of said layers being one less than the number of concentric circles.
 9. A method according to claim 2 in which twist holding means is applied to the set to retain the twist in the set as the oscillatable housing is rotated in said second direction.
 10. A method according to claim 2 including the further step of feeding a plurality of such sets together to form a bundle.
 11. A method according to claim 10 wherein the wires of at least some sets are given a different twist from the wires of other sets, so that the wires of at least some sets of wires in the bundle have a non-parallel relationship with the wires of other sets of wires in the bundle.
 12. A method according to claim 11 wherein the plurality of sets is twisted together to form a twisted bundle.
 13. A method according to claim 10 wherein a sheath of insulating material is extruded around each set to form a plurality of sheathed sets, the sheathed sets are fed together into an extrusion apparatus and a jacket of insulating material is extruded around the sheathed sets.
 14. A method according to claim 10 wherein one of said plurality of sets provides a core and the other of said plurality of sets form layers around said core.
 15. A unit for the continuous production of an electric cable comprising a bundle of sets of twisted together electric conductor wires in which each wire in a set defines a helical path about the longitudinal axis of the set which reverses periodically in direction in a predetermined manner, which comprises a plurality of devices each having an entrance housing and spaced apart therefrom an exit housing; a plurality of flexible elongated tubular sleeves continuous from end to end of a low friction material; each device having a longitudinal axis about which said wires are twisted through an angle greater than 360*; said sleeves being entrained from end to end between and supported at their ends by said housings; said entrance housing being rigidly mounted and said exit housing being mounted for oscillatory movement about said longitudinal axis of each said device to twistingly rotate the sleeves through an angle greater than 360*; means for continuously feeding electric conductor wires to and through said tubular sleeves as the sleeves are twistably rotated said devices being aligned so that the sets emerging from said devices can be fed together, and means for feeding said sets together to form a bundle.
 16. Unit according to claim 15 including means for applying twist holding means to each set substantially at the points where the direction of the helical path of each wire in a set is reversed in direction.
 17. Unit according to claim 15 including means for twisting the plurality of sets together to form a twisted bundle. 